1. Field of the Invention
This invention relates to a method of producing metallic bar stock, where a primary product of substantially regularly round or angular cross-section is first of all fabricated by continuous casting and subjected to a forging operation, and this primary product is then deformed in cross-section to the final dimension corresponding to the bar stock by means of shaping.
2. Description of the Prior Art
For producing bar steel it is already known to prefabricate a primary product by continuous casting, and in a subsequent rolling process shape it into the finished product with a desired final dimension, where it is necessary, however, to achieve a reduction of the cross-section of about 8:1, so as to convert the coarse-grained cast structure of the primary product into a fine-grained structure providing the required mechanical properties of the bar steel. Since on each rolling stand, i.e. with each forming step, rolling can only lead to a reduction of the cross-section of about 1.2:1, a plurality of passes or rolling stands is required, until the desired reduction of the cross-section of about 8:1 has been achieved. This high rolling expenditure is unjustified for high-quality material, which is only required in small amounts, and in addition the large reduction requires large casting cross-sections, which in turn increase the expenditure for the continuous casting plant.
In accordance with U.S. Pat. No. 4,930,207 A it has already been proposed to subject the primary product to a forging operation, to prevent the formation of segregations and shrink holes in the interior of the strand material due to the solidification, for which purpose forging is effected during the transition of the core portion from the liquid phase into the solid phase and is performed with a forging frequency adapted to the casting speed and with tools adapted to the width of the liquid core portion. This type of forging specially applied for preventing segregations and shrink holes does, however, not lead to a change in the actual material structure, i.e. the crystalline structure of the strand material, so that here as well the primary product has a cast structure after forging.